DIscovered this game through Voice of Dog's streams. I'm about 10 hours in now and loving evert second of it!
But, uh, where is this "secret door" that gets mentioned in the sewers. I've been through the downtown district and didn't find another sewer entrance.
Viewing post in Weird and Unfortunate Things are Happening comments
If you go west by a store that says ESBY TOYS and continue west (ignore the northern path for now), you'll reach an area that seemingly dead-ends. Search around the walled-off area where four benches face a tree and you should find the entrance to the secret second sewer.
Hope that helps, and I'm so glad you're enjoying the game :DDD